1. Technical Field
This invention relates to imaging spectrometers and, more particularly, to an all-reflective imaging spectrometer with an all-reflective objective module and an all-reflective spectral module.
2. Discussion
For certain strategic, scientific and resource sensing applications, there is a need for optical systems capable of forming high resolution pictures in a large number of different wavelength bands. Imaging spectrometers are instruments capable of providing these functions. Typically, an imaging spectrometer is composed of an objective or imaging optical module, which forms a scene image at a slit, and a spectral optical module, which receives and collimates the line field of view from the objective, disperses or separates the radiation as a function of wavelength, and images it onto a two dimensional detector array. One dimension of the array contains spatial information, while the other contains spectral information. The entire instrument is then scanned in a direction normal to the slit to cover a large spatial scene.
Current existing spectrometers include an objective optical module and a spectral optical module. Also, it is known to utilize a double pass technique in the spectral optics. Generally, these spectrometers have utilized all-refractive or refractive and reflective components. These refractive systems have several disadvantages. Some limitations of refractive systems are chromatic aberration, spectral limitations, defocus with temperature change requiring compensation, potential high narcissus, and high cost associated with the complexity and expensive refractive materials.